1998 S-10-E Electric Truck

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EV1 System 110 Inverter/Drive train

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DTC
Dianostic Trouble Codes

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1998 S-10-E Electric Truck
EV1 System 110 Inverter/Drive train

DTC-279

The S10E reported DTC-279 code upon acquisition c2008.  Upon
investigation we found resistance on the HV (high voltage) negative
battery box connection to the PIM when linked 
to chassis ground.  A 200 ohms scale was used for this test.

In the first phase we tested the circuit by “unplugging” all the connectors from 
the overall PIM when it was still in the vehicle and continued to get 
resistance readings from the HV negative connector to chassis ground.  In 
the second phase we removed the PIM from the vehicle, retested 
and received the same results.  We then went to the third phase
and, with the PIM out of the vehicle, physically 
inspecting the interior of the PIM.  Then removed the accessory 
modules from the PIM, retesting with each removal.  When we
removed the power  steering control module (PSCM) from the bottom
of the PIM the resistance reading to chassis cleared.

We subsequently opened the PSCM and retested, seperating the 
top half PSCM PCB from the bottom half and reconnecting to the PIM, and the 
resistance reading reappeared.  The DTC-279 is now located
to the top half of the PSCM.

After disassembly of the PSCM and retesting the resistance reading
vanished.  We found  that mostlikely one of the two regulator chips had a
fault-to-ground at its insulated mounting screw.  The insulator was
replaced and the PSCM has been returned to 
service functioning properly.

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-- pictures to follow --